HELP! - 1990 Escort GT Idle High at 2000 rpm

Hello,
Pulling KOEO codes 41, 42, 65 and 86, lean condition, no EGO switching, etc. all likely related to the same problem, unmetered air.
I think I have covered most of the bases here... with the engine base
timing at 10d bdc and the throttle set up to ~1000 rpm with IAC unplugged, when I plug the IAC back in the car idles at ~2000 rpm (the spout connector is also back in). Because I find 2000 rpms annoying at a stop, I have been setting the throttle plate adjustment out of spec to keep the idle down to 1500 rpms, which I find at least bearable.
The only next step I can think of is pulling the fuel rail out and installing new O-Rings, rubber fittings, etc. on the original injectors. Replacing them is too expensive ($200+), and from what I read in this ng, highly likely a waste of money.
I have been stumped for a while on this, but here is a summary of my findings, looking for input on where to go next.
1. Temporarily plugged up the accessory manifold vacuum line on the intake manifold (cuts off the cruise control, brake power assist), no change in idle. The fuel regulator and line holds vacuum, no air leaking.
2. Temporarily plugged up the PCV intake on the throttle body, no change in idle. Picked up a working canp solenoid from the junkyard and installed (numbers matched, original was bad), holds vacuum. New PCV valve and grommet (tight fit).
3. Just to be sure, temporarily disabled the EGR system by unplugging the EGR valve and EGR solenoid, no change in idle. I wanted to do this because the backpressure line from the vacuum regulator to the exhaust manifold is broken, but I am pretty sure that just means that that the vacuum regulator is not varying the vacuum signal to the EGR valve, but the effect to the EGR system is unknown to me (no vacuum, full vacuum?, passed NJ state emissions regardless).
4. Inspected the vane meter to intake tube for pinholes and cracks, etc., none found.
Unless I missed another vacuum subsystem (A/C?), it seems like I eliminated all of the vacuum lines as a possible source of unmetered air.
5. Installed a remanufactured vane meter I found in the junkyard, picked up real cheap. No change in idle.
6. Installed a new coolant temp sensor, no change in idle.
7. Replaced IAC solenoid and TP sensor last year, no change in idle.
8. I sprayed some carb gumout on the injectors while the engine was running, no increase in idle, but IMO not really convinced if this would prove anything (i.e., whether or not the injector O-rings are bad).
9. Fuel pressure checks out OK with the engine running and key off at 35 PSI.
10. Checked the upper manifold to lower manifold bolts, throttle body bolts, all tight.
Any ideas?
Thanks in advance, Matt
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Hi Matt The iac will control the idle. I did how evr noticed you did change this part but it could be faulty. Have you checked your sensor in the exhaust? This might be another problem.
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I replaced the EGO earlier this year. I don't think it is the IAC, the idle speed is the same with it plugged or unplugged into the ECA.
I am considering pulling the injectors and installing new O-rings, test resistance, etc., but might also pull the upper manifold off to look for cracks. Makes it easier to work on the injectors, too.
I was also considering the coil and ignition module as possible culprits, but not sure that these components could increase the idle speed.
Thanks for the reply, Matt
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1. unplugging and seeing idle NOT CHANGE tends to show that MAY be the problem!
- I'm referring not to not just the solenoid itself, but also to the valve it controls, - with IAC valve removed from throttle body, plug the passages and see if idle changes
- take it apart and clean the carbon gunk out of it before you dismantle the topside of your engine and remove solenoid from valve, leave plugged in and see if solenoid moves
2. Coil and ignition parts dont affect idle if engine is otherwise running smoothly
3. The O2 sensor is NOT likely the problem
Suggest also reviewing your engine 101 then go to the library and read Probst on Fuel injection.
Matt opined in

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Doesn't the car stall when you unplug the Iac? I tried it and thats what happens I think yours Matt is faulty or pluged try anonther one.
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ledpeddle opined in

Maybe I didnt make myself clear... IF there is another vacuum leak, unplugging the IAC solenoid would not change the idle speed as it would close down anyway to try to throttle down.
HOWEVER.. if the valve is stuck, then unplugging it wouldnt prove anything either. The ONLY way to rule that out is to remove the valve itself and plug the passages... especially the one on the engine side of the throttle.
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Yes, the car should stall, but only after 120 seconds or so, depending on your model. The 120 seconds is the time you are given to adjust your throttle stop screw. That is according to my emissions decal idle set procedure.
The one I have is only a few months old, when I replaced the old one with it the same high idle condition has persisted to the present day. They are about $65 so I already wasted that I don't want to again. If there is something wrong with the IAC it is probably the signal it is getting from the ECA, I just don't know yet.
I am going to try some carb gumout on the throttle body near the butterfly valve, maybe air is getting in there. I was thinking about the propane experiment mentioned in this ng, but not sure if that is really safe.

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Hello Backyard,
As you suggested, I can try installing a blocking gasket under the IAC to see what happens... but
I've given up on the IAC as a possible cause. I gambled on a replacement a few months ago and no change at all in the idle condition, so no carbon build up like the old one had. I could put the old one back on and be in the same spot.
I can unplug the IAC and set the throttle plate to 1000 rpm, but that results in 2000 rpm when I plug the IAC back in, so I back off the set screw to get the idle to 1500 rpm because I find 2000 rpm at a traffic light to be really annoying.
Maybe the IAC is getting a bad signal from the ECA, but I don't know what the voltage range should be for a given rpm value or I would measure it.
If there is an air leak in the charging assembly, setting the throttle stop to 1000 rpm is probably meaningless anyway.
A tear down and inspection of the intake would only cost me the replacement gaskets and o-rings, but I would rather skip the self-inflicted labor if I can.
A real stumper, I wish I had a breakout box!
Thanks for the reply! Matt


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I give up... here is what you have said... everything else deleted.
Kind of hard to follow with helpful info like this
Good Luck!
BM out.
Matt opined

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I see what I did...
To explain, I have had this problem for over a year now but I have always been able to run the car at 2000 rpm for 2 minutes, unplug the IAC, set the throttle stop to 1000, plug the IAC back in. This is all per procedure on the emissions decal. I can still set the throttle screw using this procedure and just did it the other day.
Which was also when I was checking again for any possible source of air leaks, malfuctions, etc., and one of the quick tests I performed was unplugging the IAC at some random time when the engine was running. On this one occasion there was no change in the idle speed. Not sure why this was, maybe I plugged it back in before it could drop.
Regardless, the IAC plugged in is adding 1000 rpm to the idle speed, which I am thinking could be either a percieved increase due to an air leak elsewhere, or a real increase because the IAC is getting a bad signal.
I've already gambled on a new part and the same symptoms exist with the old one, so I am not thinking the unit itself is bad.
Thanks! Matt

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Does anyone know if there is a vacuum connection to the A/C apparatus on this vehicle? If so, what/where does it tap into on or near the engine?
Thanks! Matt
snipped-for-privacy@optonline.net (Matt) wrote in message

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Hey Matt did you check your EGR it might cause this also check your pcv it may be plugged. Try resetting the computer and see what happens. I would think the EGO sensor is faulty. Mine, when its cold revs almost 2,000 rpm and then drops to below 1,000 I would tend to think that that is the problem telling the motor to rev. It is probaly saying the motor is cold all the time. So the computer keeps it reving high. look up in google for the way to test your EGO sensor there is a way with a meter. Also the air charge sensor maybe it bad.
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I installed a new pcv and grommet, tight fit and the valve is working. I cut off the pcv intake to the throttle body using a rubber cap, no change in idle.
In fact, I cut off all of the vacuum intakes to the throttle body or intake manifold: accessory vacuum, egr, pcv... no change.
I gambled on a new ego earlier this year, same codes, same condition are present. Also put in a reman vane meter I picked from the junkyard, no change.
I am thinking that this is a non-EEC-IV problem, but not sure how to go about limiting my liability of a complete tear down and rebuild of the whole air charging assembly. I would rather find the problem first before I start taking more stuff apart. Replacing the ECT on the rear heater tube was bad enough.
I am at the point of considering the propane method suggested by backyard.
Thanks, Matt
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Matt opined

It wont "blow up"... just use it outside, light the torch adjust for medium non-blowing flame, then snuff it out.
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Being propane, would this increase the idle of the car if it finds its way into the intake, or would it cause the idle to decrease? I had to break out the propane torch to heat up the heater tube to get the old ECT out, so it is still within sight of the toolbox...

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I TOO HAVE HAD THIS PROBLEM. AFTER LONG AMOUNTS OF TESTIN AN CHANGIN BITS THAT DIDNT NEED TO BE CHANGED I THEN FOUND OUT THAT MY E.C.U. WAS KNACKERED
ONLY DONT TAKE MY WORD FOR IT I NEEDED A MAIN DEALER TO TELL ME THAT!!!!
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Hello Transit Man,
I have heard that EEC-IV systems can lose control of the idle after a while, but don't know much about that thread.
I would like to get a donor 1990 ECU but the local parts picking ground does not have any 1990 wrecks at the moment. I can get a donor 1989 GT ECU for my car, but not sure if their are differences between them that would affect the car in other ways.
I'd at least like to try a swap to see what happens, but at about $200 for a new ECU, I'd rather not invest that much for an experiment, and just get one on the cheap from the local pick & pull. I'll post an update if/when this happens.
Thanks, Matt Matt
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ONLY TROUBLE WITH THAT IS YOU ALSO NEED THE KEYS PROGRAMMED TO THE E.C.U. AS IT HAS AN INTERGRATED P.A.T.S. (PASSIVE ANTI-THEFT SYSTEM) MODULE INSIDE!!! BUT IF U CAN GET A DONOR ONE THAT HAS THE SAME SPEC AS URS BY ALL MEANS GIVE IT A TRY!!!
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I don't have power locks or an electronic key so wouldn't this be a simple drop in replacement?
Thanks, Matt
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OH WELL IF U HAVE NO CHIP IN THE KEY THEN IT SHOULD BE ESY ENOUGH TO THROW A REPLACMENT IN!!!1
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